googleapis/mcp-toolbox · error

bucket cannot be empty for tool %q

Error message

bucket cannot be empty for tool %q

What it means

Same validation as the get-bucket-iam-policy tool: cloudstorage-get-bucket-metadata's Initialize rejects a bucket field that is present (non-nil pointer) but an empty string. Either supply a real fixed bucket or omit the field so it becomes a tool parameter.

Source

Thrown at internal/tools/cloudstorage/cloudstoragegetbucketmetadata/cloudstoragegetbucketmetadata.go:72

	tools.ConfigBase `yaml:",inline"`
	Type             string                 `yaml:"type" validate:"required"`
	Source           string                 `yaml:"source" validate:"required"`
	Annotations      *tools.ToolAnnotations `yaml:"annotations,omitempty"`
	Bucket           *string                `yaml:"bucket,omitempty"`
}

var _ tools.ToolConfig = Config{}

func (cfg Config) ToolConfigType() string {
	return resourceType
}

func (cfg Config) Initialize(context.Context) (tools.Tool, error) {
	if cfg.Description == "" {
		return nil, fmt.Errorf("description is required for tool %q", cfg.Name)
	}
	if cfg.Bucket != nil && *cfg.Bucket == "" {
		return nil, fmt.Errorf("bucket cannot be empty for tool %q", cfg.Name)
	}

	allParameters := parameters.Parameters{}
	if cfg.Bucket == nil {
		allParameters = append(allParameters, parameters.NewStringParameter(bucketKey, "Name of the Cloud Storage bucket to inspect."))
	}

	return Tool{
		BaseTool: tools.NewBaseTool(
			cfg,
			tools.GetAnnotationsOrDefault(cfg.Annotations, tools.NewReadOnlyAnnotations),
			tools.Manifest{Description: cfg.Description, Parameters: allParameters.Manifest(), AuthRequired: cfg.AuthRequired},
			allParameters,
		),
	}, nil
}

var _ tools.Tool = Tool{}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Set a concrete bucket name, e.g. `bucket: my-bucket`.
2. Remove the `bucket` key so the bucket becomes a required invocation-time parameter.
3. Pre-validate config strings for emptiness after environment expansion.

Example fix

# before
bucket: ""
# after
bucket: my-gcs-bucket

if cfg.Bucket != nil && strings.TrimSpace(*cfg.Bucket) == "" {
    return errors.New("bucket cannot be empty; set a name or omit the field")
}

func bucketProvided(cfg Config) bool { return cfg.Bucket != nil && *cfg.Bucket != "" }

When it happens

Trigger: cfg.Bucket != nil and *cfg.Bucket == "" at Initialize — YAML `bucket: ""` or programmatic tools.Ptr("").

Common situations: Empty env-var substitution into the bucket field; YAML key present with no value; generated configs with unset placeholders.

Related errors

• bucket cannot be empty for tool %q
• bucket cannot be empty for tool %q
• invalid source for %q tool: source %q is not a compatible ty
• description is required for tool %q
• description is required for tool %q

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/cf839e4793ef577f. Report an issue: GitHub.